Adsorption of a base material into fibers is conducted to facilitate release of soil components from the fibers at the time of washing. When soil components are easily released from fibers at the time of washing, an extremely excellent washing effect can be brought about as compared with a usual washing method. Such effect is called a soil release effect, and the base material exhibiting this effect is generally called a soil release agent.
With respect to the soil release agent, several findings have been obtained, and for example, Japanese Patent Application National Publication (Laid-Open) No. 2001-502735 discloses a soil release agent containing a crosslinked, nitrogen-containing compound obtained by crosslinking a compound having at least 3 NH groups with a bi- or more (poly) functional crosslinking agent reacting with NH groups, and Japanese Patent Application National Publication (Laid-Open) No. 11-508319 discloses a soil release agent containing a modified polyamine compound. These soil release agents exhibit an excellent effect on hydrophilic cotton fibers, but cannot give a sufficient effect on hydrophobic synthetic fibers such as polyester.
On one hand, a compound based on terephthalate is known to be effective as a soil release agent for hydrophobic synthetic fibers such as polyester textile blend cloth etc. (U.S. Pat. Nos. 3,416,952, 3,557,039, and 4,795,584). However, these soil release agents do not exhibit a sufficient effect on comparatively hydrophilic cotton fibers.
U.S. Pat. No. B 6,083,898 discloses a crosslinked product of polyethylene imine and polyethylene glycol diglycidyl ether. U.S. Pat. No. B 6,071,871 discloses a polyoxyalkylene adduct, quaternarized product and betaine compound of a crosslinked product of polyethylene imine and polyethylene glycol diglycidyl ether.
As described above, a soil release agent capable of exhibiting an effect on both hydrophilic fibers such as cotton and hydrophobic fibers such as polyester has never been found.